The present invention relates to a method for compatibly increasing resolution in television systems. Such a method is based on a system for increasing resolution as disclosed in an article by Broder Wendland entitled "Entwicklungsalternativen fur zukunftige Fernsehsysteme", published in Fernsehund Kino-Technik, Volume 34, No. 2/1980, pages 41-48.
Present-day color television systems still have room for improvement in picture reproduction quality. Due to the single-channel transmission of the luminance signal and the modulated chrominance subcarrier, the added capability of reproducing colors results in a reduction in quality compared to the old black and white transmission systems. The effective resolution in the luminance channel of such systems is about 4 MHz (with reference to the 625-line standard).
With respect to future color television systems, it appears to be desirable to improve picture quality beyond its present state in a manner that is compatible with already existing systems.
A method of offset sampling with the aid of prior and subsequent planar filtering and full frame display is described in the above-cited publication in Fernseh- und Kino-Technik, Volume 34, No. 2/1980, pages 41-48 to compatibly improve detail resolution. The technique of offset sampling is also described, inter alia, by Mersereau in "The Processing of Hexagonally Sampled Two Dimensional Signals", published in Proceedings of IEEE, Vol. COM-27, Aug., 1979, pp 1239-1247. This method permits a considerable increase in horizontal resolution. Quality improvement in the vertical direction is attained by full frame reproduction. Compared to older papers on the subject of offset scanning (e.g. "Investigation into Redundancy and Possible Bandwidth Compression in Television Transmission", Philips Research Reports 15, 1960, pages 30-96), the use of prior and subsequent planar filtering and full frame display results in a fault-free increase in resolution in appropriately improved receivers.
With selection of a sampling method in the form of pulse amplitude modulation for signal transmission, the quality in the compatible receiver still suffers to a certain degree: the additional information present in the signal for detail resolution results in an additional 25 Hz flicker interference in existing systems (in 60 Hz systems, 30 Hz flicker interference). Insofar as the information for luminance and chrominance is not transmitted without crosstalk, offset sampling produces further crosstalk problems.
An article entitled "Multiplexed Analogue Components-A New Video Coding System For Satellite Broadcasting", by R. Rawlings and R. Morcom, published in Electron. Eng. Assoc., IEEE Conference, Brighton, England, Sept. 18-21, 1982, IBC 82, International Broadcasting Convention, XVI+376 P., at pages 158-164, discloses the reduction of space-time alias effects produced by the folded down high frequency spectrum in that the signal amplitude of the high frequency spectral components is lowered before folding down.